Variable pitch propeller mechanism for winged aircraft



May 29, 1956 EMRULLAH ALI YILDIZ 2,747,675

VARIABLE PITCH PROPELLER MECHANISM FOR WINGED AIRCRAFT Filed Aug. 1, 1952 5 Sheets-Sheet 1 1 N VEN TOR EMRVLLFA /74/ y/40/z BY fax/v AM ATTORNEYS VARIABLE. PITCH PROPELLER MECHANISM FOR WINGED AIRCRAFT Fild Aug. 1, 1952 May 29, 1956 EMRULLAH ALI YILDIZ 5 Sheets-Sheet 2 ATTORNEYS May 29, 1956 EMRULLAH 311.1 YlLDlZ 2,747,675

VARIABLE PITCH PROPELLER MECHANISM FOR WINGED AIRCRAFT Filed Aug. 1, 1952 1 5 Sheets-Sheet 3 BY Paw/0 w- M ATTORNI'Ys May 29, 1956 EMRULLAH Au YlLDlZ VARIABLE PITCH PROPELLER MECHANISM FOR WINGED AIRCRAFT 5 Sheets-Sheet 4 Filed Aug. 1, 1952 5 INVENTOR fMKUM/a flu WLa/Z,

ATTORNEY6 May 29, 1956 EMRULLAH Au YILDIZ 2,747,675

VARIABLE PITCH PROPELLER MECHANISM FOR WINGED AIRCRAFT Filed Aug. 1, 1952 5 Sheets-Sheet 5 BY f n m ATTORNEXQ;

United States Patent VARIABLE PIICHRROPELLEKMECHANEM O WINGEDJFAIRCRAFT Emrullah an Yildiz, Istanbul, Turkey Application August 1,-1952,Serial'No.- 302,046

sctaims. euroltars descent for landing. It is also arr'object-of the invention to accomplish the same purpose during -take=otf.

*A further object'ofthe invention is tto enablewinged aircraftto operate at m'uch lower and safersspee'ds during inclined descent in landing than possible withaconventional variable pitch propeller, mechanismsfand wving flaps,

and also to permit slower ground speed arid i shor-ter ground path after landing.

It is a further object of the inventiomtoaenable:zwinged aircraft to ascend from take off at slower. speedr-r-thanewith conventional variable-pitch propeller: mechanism: but with increased effective propeller power.

- A further object of the invention is tozprovideimproved variable pitch propeller "mechanismkfor winged i aircraft wherein individual-upright. propeller blades ".are-zgchanged in pitch successively insteadofszsimultaneouslym'arid in accordance with.v their. rotative: position. n Itisparticularly proposed to increase the pitch ofxpropeller.bladeszduring rotation downwardly and. cause-the-bladesno ,exert'flown- :ward thrust and give additional lift.

It is a further-object .of-vthe,.-inventionq-to cause'propeller blades to operate at 'diflerent pitches. during-rotation downwardly and upwardly.

Conventional:adjustable, pitch-mechanism. forr=aircraft propellers of the class referred :to servevto'varytthemitch of the: propeller; blades;.in;. unison. Ghangesain the; pitch of all the. blades is reflected simultaneouslyfondifferent flight conditions. The :blades all; operate aosomeasame =selected :greaterpitch during-: aScent randadescentsthan their. pitch, during normal horizontalnflight.

.On the other hand, according totthepresent invent-ion provision is made .for. tautornaticallynvarying :rthe g pitch of the propeller blades individuallyzsothat eachtbl-adegoper- :atesat .diiferent; pitchessin-the courseofarotationp inlairlcraft: descent:andlor-iascent. Brovisiondsiurtheri made for rotation of allszpropellerhblades at arcommon niitch duringnormal horizontals flight. -!PI'OiSiOIlt1iS further made: for-varying. the .-pitc-h @oftthepropellerblades fomall flight conditions nnder=.manualmcontroltiofnthenaircraft 1 pilot.

It is ,further .conternplatedttovarytthe -rpitch .ofsaircraft propelleriblades;dnringnthe course of rotation without objectionable vibration 1 efiects. To this rend .iiti. is proposed a to employ multiple,propellersaand .to. rota v ellers-onv oppositesides of. .ansaircraft about opposite rotational orbits. Two, four.orsotherneventinumber..of propellersmaysthusly be operated.

ltislfurther. proposed:.to;incorporate special meansin .conjunction with automatic pitchvarying mechanism'ffor preventing.vibration..from .developingsinrsuchl mechanism.

2,747,675 Patented May 29, 1956 I CC zThtarforegoingz and other :objects :andJnenefits :of theinvention iwillrrbe understoodgfrom theraccompanying :drawringsiizand-xrthemetailediidescription thereof to;follow. In

such adrawings 5 1 tistazfronnview of; an 'aircraftxpropellen accordtiingzto-ithex inventiona with-z all the :blades at the; same. pitch for normal horizontal flight;

:Fig. .2 :is was isimilar .view; of the 1 same :propeller -with rzthevpitch of: the blades ehangingin c diflerent portions of 19 :Etheir r-rot-ational orbit; during-aircraft descent and/or,.: as-

I, eent;

:Fig. S3 isuagtdiagrammatic view ofnthe transverse-plane of rotation of a propeller according to the inventionfind :indicatin g difi?erent 1portions,.of the rotational orbit; 15 :Eigs. 4; 5, 6sar1d 7- :are diagrammatic views illustrating :the dilferentpitehofipropellenblades zit-different portions ofxthe rotational orbit of; Fig. -3

Fig$8 isa'l-more or-ilessdiagrammatic front view of .,an;aircraft;with multiplepropeller. mechanism according to. the presentinvention;

::Fig. 9 is; a; top plan view v of the aircraft shown .in Fig:

g :10; is}.aefragmentary'-;1ongitudinalvsection of one ..;forn 1-of-variable pitch propellerblade according to the invention;

*Hg. 11 is;--a transverse-.section of: a.- variable gpitch prospeller blade taken-at knell-11 oftE-ig;v

-'Eig.;;,l2 is a ,Jsvottorrn planwiew' of; automatic; propeller pitch;-v ar-ying mechanism according to -the invention; :tFig. 113 ,is a iside-zelevationof the, mechanismwshown rin Fig. 12;

iFig;= 1:4:is-a 'front view ,of the'mechanismshown in Fig. 12, butwvithflthe; propeller t omitted;

tliiga-liiis a fragmentary top plan view of; certain of wthet operating parts; shown insliig 12;

=.=Eig.; :16. is'r an -enlarged fragmentary viewpartly -in section and partly in elevation of the cam trackiand asso- -.-ciat,ed;-.-pa1:-ts;

' *ari endiview of the roller bearing: mechanism a Fig. 18 is ajpla view, of; the complete operating linkage mforaone blade= of a;;propeller;

fig. 919;;is ornewhatt-diagrammatic top view; partly in: section-of ne --form-of ;manual controlfor :adjusting titl 12K6 vat fla mew han s J .2-0 is za side -.e leyation; of thecontroharm shown -win1 His, -9; nd,

:iFig. .2131s a gfront eleyation;of;the: control arm and associated parts. 'iThe variablemitch propellen nechanism of the invenjtion may tbe employed with .propellers having-.- two,- three ,;or,- -more;=blades. Forpurposes.refillustration I have selected threeebladed propellers. One. of snch propellers .i.:is' shown;in Figs. Land-52. tflheith-ree blades thereof are generally= designated ZA B andC. As-ibest ;shown in 1 Figs. ,lltandjjl-i such.blades are mounted 011528. rotatable ahub 10;;seeured to the jorward end of rotatable propeller sha Hfl- 1 r m ath .sha t-c n c i qany Suit- -a l t -yp i fd 'iV HEEmQIQI n t nacheof the-propeller blades is formed; in two sections "which are hinged together alongasubstantially'radial ne. T he; prward-pryleadssection -ifl of eachvblade is gidly; moi mtedw pnelgub (1Q a t;a pitch isuita-ble for normal q orizontaL-flight. ,The a ngle pf pitchmaydepend-gnpon (t5-,t l;ar ious.factors such,as the sizegof the tblade power of the motor and size and weight of the.aircraft. A .pitch nangleof 45 .,,.,is..he re takeriiorillustration. .Eachblade ,QaISO iHCIIldCS a trailing flap section '14. whichis variable *inQPittth imr'elation tq section'12. Any suitable, means 70,v may' be employe'd'for' hinging the two blades sections toge'ther. jAsgshown' in Ei gsglO and ll the forward edge .a6fftlan ct pn1 maybe p ov de with ase iesbf mac '2 \J recesses 15 at recurrent longitudinal points. Anchored in such recesses are I-bolts 16. Similar I-bolts 17 are secured to the arcuate rear edge of front blade section 12. Hinge bolts 19 secure bolts 16 and 17 for hinging movement of flap section 14 relative to front section 12;

Preferably forward blade section 12 inclines slightly forwardly in the direction of rotation, say at an angle of and also tapers outwardly. See Figs. 1 and 2. Preferably flap section 14 also tapers in an outward direction. See Fig. 1.

In normal horizontal flight of an aircraft flap section 14 will be aligned with and have the same pitch as section 12. In Fig. 1 the sections ofeach of the blades A, B and C have the same constant pitch during normal horizontal flight, say 45, as mentioned above. See also Fig. 4.

In descent for landing the flap section 14 of each propeller blade is progressively changed relative to front section 12 in the course of rotation thus changing the effective pitch of each entire blade. is to so increase the pitch of each flap section 14 during downward movement as to cause the air to be forced in a downward direction. Effective lift is thus produced to supplement the lift of the aircraft wings. For convenience, pitch angle is measured from the rotational plane of the propeller. When the pitch of flap section 14 is increased relative to such plane it increasingly decreases relative to the rotational axis.

At and near the top of the path of rotation, designated 0 in Fig. 3, each flap section 14 will be aligned with each of the front sections 12. See Fig. 4. As each blade rotates downwardly the pitch of each flap section 14 is progressively increased and will reach a maximum pitch at or about the time it is in the horizontal position designated 90 in Fig. 3. increase will be subject to adjustment by the aircraft pilot to suit conditions. At maximum pitch each flap section 14 may have a pitch of as much as 75 representing an increase of 30 from the pitch of front blade section 12.

During the lower half of its downward movement the pitch of each fiap section 14 progressively decreases until it is at the same pitch as front section 12 at the bottom of its movement, designated 180 in Fig. 3.

It is further proposed to vary the pitch of each fiap .section 14 as it rotates upwardly, but the pitch will be changed reversely to the change during downward movement so as to decrease the pitch of each flap section relative to front section 12. During the first half of its upward rotative movement the pitch of each flap section 14 is progressively decreased and reaches a minimum pitch at or near horizontal position, designated 270 in Fig. 3. See Fig. 7. During the last half of its upward rotation the pitch of each flap section 14 is progressively increased until it reaches the same pitch as front section 12 at or near the top of its movement.

As has been explained the flap section of each blade progressively changes pitch during the course of rotation for landing descent and also for take-off ascent. The pitch of the flap sections of blades A, B and C will progressively change in relation with each other during the course of rotation. In Fig. 2 flap section 14 of blade A in horizontal position is shown at maximum pitch. Flap section 14 of blade B is in the first half of its upward movement from bottom position and is starting to decrease in pitch. Flap section 14 of blade C has passed horizontal position in its upward movement, at which it was at minimum pitch, and is again approaching the same pitch as front section 12.

The automatic pitch varying mechanism for changing the effective pitch of the blades A, B and C by changing the pitch of their flap sections 14 is associated with pro peller shaft 11 and hub 10. A non-rotatable annular cam track member 20 is journaled by a hub socket comprisingintegr'al socket portion 21 and socket pieces 22 The essential purpose See Fig. 5. The amount of pitch and 23, which are removably secured to track member 20 by bolts 24 and 25, on a rotatable annular knuckle- 26 fixed to shaft 11 in rearward spaced relation to hub 10. See Figs. 12, 13, 14, 15, 16 and 17. In normal. flight track member 20 will be perpendicular to shaft 11.v See Figs. and 16. In such position it will be parallel to the plane of rotation of the propeller blades A, B and C. From such position track member is adjustably' tiltable on knuckle 26 about an upright axis, either ver tical or inclined up to, say, degrees from the vertical, being supported for such movement by means hereafter referred to. When tilted track member 20 is adapted to effect pitch variation of the blade flap sections 14.

The peripheral portion 27 of track member 20 is of' hollow curved cross-section and has track surfaces 28 and 29 on which roller bearings 30 and 31 are adapted to ride variously, depending upon whether the track member is. in non'tilted or tilted position. See Fig. 16.

Roller bearings 30 and 31 are mounted by journals 32. and 33 on the reduced outer end portion 34 of an arm 35.. The inner end of such arm is pivotally mounted in bifurcated supporting element 36 secured to hub 10. See Figs. 16, 17 and 18. Pivotally connected to the outer end of arm is the rear end of a further arm 37 which extends forwardly in outwardly spaced relation to the hub. Pivotally connected to the forward end of arm 37 is an actuating rod 38 adapted to be rigidly secured to one of the propeller flap sections 14. Also pivotally secured to the front end of arm 37 is the rear end of a further arm 39. Such arm extends forwardly in alignment with arm 37 and at its forward end is pivotally connected with the outer end of transverse arm 40 of a bellcrank. The bellcrank is pivotally mounted by bifurcated supporting element 41 on the front end of hub 10. These variousv parts merely rotate with hub 10 when cam track member 20 is in non-tilted position. When the latter member is tilted, as in Figs. 12, 13 and 15, such parts under actuation of roller bearings 30 and 31 riding in peripheral portion 27 have a forward and backward movement to change. the pitch of one of the propeller blade flap sections 14.

Centrifugally responsive means is provided to stabilize the variable pitch propeller mechanism against vibration just described under rotation of the mechanism and the air force acting on each flap section 14. Pivotally supported in a bifurcated supporting element 42 on the forward end of the hub diametrically opposite supporting element 41 is a forwardly extending arm 43. To the forward end of arm 43 is secured a relatively heavy metal ball 44 or equivalent weight element adapted to be urged laterally outward on arm 43 by centrifugal force under rotation of the hub. Located. forwardly of the hub is a transverse'arm 45 pivotally connected at one end to an intermediate portion of arm 43 and similarly connected at its other end to the forwardly extending arm 46 of the bellcrank. The centrifugal force developed by ball 44 through arms 45 and bellcrank arm 46 constantiy urges bellcrank arm 40, arms 39, 37 and 35 and actuating rod 38 in a forward direction. Such arms and flap 14 are thus maintained against vibration and roller bearings 30 and 31 are maintained in proper engagement with peripheral portion 27 of track member 20.

The pitch bearing mechanism just described is shown in Figs. 12 and 13 in connection with flap section 14 of propeller blade A. Similar separate actuating mechanism duplicating the parts shown in Fig. 18 is provided for actuating the flap sections of blades B and C. Such parts appear in Figs. 12, 13 and 14 as 35b, 37b, 38b, 39b, 40b,

"the track member and to progressively increase and dcthe aircraft pilot.

shown in Figs. 19, 20 and. 21. -Mounted on a-vertical panel '59 in the pilots-compartment.in'an aircraft-is? a pivoted manually operated arm;-51:.having adetenti-SZ camp re crease. :the pitch. of .eachflap section .on. downwardmove- ..ment..of. each-blade and: progressively. decreasmaridrthen progressivelyincreasc -the:pitci1 ,of the .flapsection- .ofQeach blade on .upward vmovement .thereof, :as, Lheretofore..,explained inconnection-with'Figs. 3..-to 7. .lngthecourse of rotation the centrifugal. balls. 44, 44b, and .440 swing laterally. inwardlyand outwardly-to.correspondinglyraffect .theflap actuating mechanism :for. eachdlap..section..and

maintain aconstant tension, onithe. parts .of such: mechanism under centrifugal. force. a The amounhof change in pitch of theflap. sectionsv willudependupon the amount of tiltof track. member 20. For .the.:arrangement.-.of parts shown maximum. pitchwill-be.effected-when track ..mcmber.-20: is tilted. approximately. on .its.'up right taxis relative to propeller shaft :11. f If found necessary the: various flap sections 14 may tbesprovided with indentahone-48 to clear peripheralportionsfl of track member when in the extreme tiltedposition. -A. domed hollow cap 49 of sufficiently large diameter to. house' and-v protect I the parts-of the pitch changing mechanismzis secured tothe propeller blades in--outward spacedrelationuto hub 10 as shownin Fig. 12.

#The pitch.varyingmechanism is broughtsinto .operation during landing descent and take-off ascent by. .tilting of cam track-member 2i Thisis-accomplishedmanually by One control meansfor this -purpose:is

adapted to .releaseable locking. engagement with. notches in an arcuate notched blade 53. adaptedqto-retain control arrrr 51 in any adjusted-position. Pivotally-ssecuredto the lower'end of arm-51 is an adjusting rod'54 which. ex- .tends. outwardly through the aircraft+wing to a bellcrank-55. Such bellcrank issupported by a bifurcated" supportingiel-ement 56secured to a-;rigid-section interiorly of the aircraft wing. Mounted in the-forward edge of the 'aircraftwing is a bushing 58. Connecting with bellcrank 55 is a further'actuating rod 57-,which;-extendsoutwardly through the bushing and: pivotally eonnectswwith' a bi furcated supporting-elementxfi ontYQCkmBmbeE-QO. See Fig-x19. Bushing '58 should.v have ax'hollowr rectangular ,slotradapteid ito:,.closely;. embrace; the topposite: sides :of actuating rod 57 :and prevent rotationrrofrtrack:member 2% Such slot, not shown, should have sufficient widthjto" accommodate limited tilting movement of rod 57. By swinging control arm 51 .tolthe left-asseen in- Eigs. 19 and 21 the pilot can set track member 20 to any degree of tilt to produce the desired change in pitch'of the propeller (blade flap sections 14ineithendescent or ascent? Swingqing arm-51 to. the right from any;.tilted position "ofytrack member 20'Wlil cause. the track member toassurnev its inoperative. position perp,endicular --to: propeller-7,.shaft'f11 for horizontalflight. Of course. theztrack member-.smust 1 be held against rotationdnall:itszadjusted positions. ;-.Any*

suitable bracing therefore for. such puripose may be; .provided in conjunction with the mounting wing. Also, it will ordinarily be desirable to provide any suitable mounting for the track member which will pivotally support the member itself or its hub for its tilting movement about a fixed upright axis, perpendicular or inclined. Such details will be obvious to any one skilled in the aircraft art and have not been illustrated for such reason.

The variable pitch propeller mechanism which has been described should be mounted in reversely rotating pairs, two pairs or more, on opposite sides of an aircraft. In Figs. 3 and 9 is shown an aircraft having a body 59 and Wings 6!) and 61. The propeller with blades A, B and C and the actuating mechanism heretofore described is shown as mounted on the outer end of right wing 60 in conjunction with a propeller driving engine 62. A similar propeller having blades A, B and C reversely driven by a second engine 53 is mounted at the outer end of the left wing 61. The aircraft shown is merely exemplary. However, it is desirable for best results of the variable 6 .pitch propellenmechanisms. thatthe engineand propeller ...units.;should .-be located .in: the region of: the longitudinal .tcenter-eofnthe .gravity of! theaircraft. ,A' second manually .adjustableu-pitch..adjusting..mechanism similar to that .-.5 .shown in Eigs. 19.10 21 Willrbe provided for the actuating mechanism for propeller blades A, B and C on wing 61.

The pitch changing mechanism for such blades will be similar..to...that.described-except. that the actuating parts .w'ilhbe. mounted. in. reverse relation around the hub. be-

.10 :cause.of..the..dilferent direction-of rotation of the second propeller. Alsothe track member. willhave tilting move- :mentabout itsn upright. axis opposite; to that of track ...1nember. .20.

. ,Asheretofore-explained,.. the-essential. purpose of in- 15... creasing. the pitch .ofthe propeller blades during the down- -wardrotation .isto secure a substantial downward thrust .of air by. the variable pitchflapsectionsin addition to the forward; thrust obtained= by. the .forward blade sections. .1.The effect ofstheudownward. thrust of air gives a lifting 20 aeffect to.the eblades=in their downward motion which supplements-.the..lift ..,of;the aircraft wings. The forward speed of'the aircraft either. during ascent or descent is substantially lower, than with conventional variable pitch propeller mechanisms. This iscompensated by the lift .25..effecton. the-.blades. Whereas with ordinary variable mpitchmechanismand wing flapsthe forward speed during .landingdescent: is .ordinarily not lower than one-quarter .ithe toprspeedmin ,horizontal ,flight, the present arrangement-permits .landingdescent at speeds which may range .--30..-.down .to; as .;low..:as.xone.-tenth of .top horizontal flying speed.

..The...decr.ease. inpitch vofthe propeller blade flap sec- .itions below..the .-pitch ,of the frontsections provides a .feathering action which decreases the air resistance on the blades duringutheirzupwa'rd.movement. This counterbal- .jances. the increased load on the blades during their down- .ward motion. Preferablythe. decrease in pitch of the flap ..sections on upwardmovement belownormal pitch repreesented bynthezpitch zoftthe.front. sections is the same in -40.an1ount;..measured.inydegrees, as the increase of pitch above normal pitch of the flap sections on their downward .,movement. By wayofeXample, it has heretofore been suggested ,thatif .the normal pitch of the blades is the -increase inipitchon :downwardmovement ofthe flap sec- 45,.,tions..may..be.within arange of .30 higher and that the ;de crease.in..pitch of .the' blades on their upward move- .ment bewithin a.,.rangeof 30 lower than'normal pitch. ..While,.the change. in. pitch is automatically accomplished ..the changesinapitchto .suit any conditions of descentor eon/ascent.are;.manua lly adjustableby the pilot.

..lf-.,the.tiltable trackmechanism 20 is mounted for rota- ...tion upon avertical axisthe progressive change in pitch of the propeller bladeflap sections will be aspreviously explaineddn conjunction with Fig. 3 and Figs. 4 through 7. ..:Because the-airisfluid, andis given a swirling motion ..--by;the";blades;.as.welhasmotion;in a rearward direction it may be found desirable to advance'the timing of the pitch changing cycle. This may be accomplished by mounting the track sections of the actuating mechanism for tilting movement about an inclined axis. The angular advance in timing may range upwardly to, say, 30. Assuming such a condition the propeller flaps would be at normal pitch in alignment with the front blade sections at 330 on the rotational diagram of Fig. 3. The pitch 5 would progressively increase therefrom and reach a maximum at 45. From such position the propeller flaps would progressively decrease to reach normal position at 150. From such position the pitch of the flap sections would progressively decrease to a minimum at 240 and therefrom progressively increase in pitch to reach normal pitch again at 330. These figures are merely illustrative and may be subject to considerable variation depending upon propeller size and shape, engine power and rotational speed and the size and weight of the aircraft.

It will also be understood that the particular construction of the propeller blades and the variable pitch mechanism therefor as have been illustrated and described are merely illustrative and are capable of considerable variation and equivalency within the scope of the invention,

which is to be determined in accordance with the appended claims.

I claim:

1. Variable pitch propeller mechanism comprising a propeller rotatable about an axisparallel to the line of flight and having variable pitch propeller blades, each blade comprising a fixed pitch blade section and a variable pitch blade section, and automatic mechanism operable during downward rotation of the blades to increase the pitch of the variable pitch blade sections above their normal pitch and operable during upward rotation of the blades to decrease the pitch of the variable pitch blade sections below the normal pitch, further including centrifugally responsive means rotatable with the blades and exerting centrifugally developed forces on the variable pitch blade sections during increased and decreased pitch changes of the variable pitch blade sections by the automatic pitch changing mechanism.

2. Variable pitch propeller mechanism comprising a propeller rotatable about an axis parallel to the line of flight and having front blade sections and rear flap blade sections hinged to the front blade sections for change in pitch relative to the front sections, individual means for changing the pitch of the flap blade section relative to the front blade section of each blade of the propeller and common means for actuating said individual means to progressively increase and progressively decrease the pitch of the flap blade sections relative to the front blade sections during downward blade rotation and for actuating said individual means to progressively decrease and progressively increase the pitch of the flap blade sections relative to the front blade sections during upward blade rotation, further including centrifugally responsive means for each propeller blade operative to exert centrifugally developed forces on each flap blade section and its individual pitch changing means during pitch changing operations.

3. In a device for diminishing vibration of a propeller blade element having constantly varying pitch during the course of rotation, a weight pivotally mounted and rotative with said blade element so as to move away from the axis of rotation of said blade element by virtue of centrif- 11 gal force as said blade element rotates, a linkage mechanism connected with said blade element'and operable to oscillate said blade element for effecting cyclically varying pitch, and means connecting said weight with said linkage mechanism to exert a steadying influence of positive thrust on said blade element by virtue of the centrifugal force acting on said Weight.

4. Variable pitch propeller mechanism comprising a propeller rotatable about an axis parallel to the line of flight and having front blade sections and rear flap'blade sections hinged to the front blade sections for change in pitch relative to the front sections, individual means for changing the pitch of the flap blade section relative to the front blade section of each blade of the propeller and common means for actuating said individual means to progressively increase and progressively decrease the pitch of the flap blade sections relative to the front blade sections during downward blade rotation and for actuating said individual means to progressively decrease and progressively increase the pitch of the flap blade sections relative to the front blade sections during upward blade rotation, said individual means being rotatable with the propeller blades and having forward and backward movement relative to the front blade section, and the common actuating means comprising a normally stationary member extending transversely of the propeller axis and tilted about an upright axis, and further including manually controlled means for varying the tilt of said member relative to the propeller axis and for bringing said member into parallel relation with the plane of rotation of the propeller blades, said mechanism including centrifugally responsive means applying centrifugally developed forces to the individual means and to the flap blade sections during rotation.

5. Variable pitch propeller mechanism comprising a propeller rotatable about an axis parallel to the line of flight and having front blade sections and rear flap blade sections hinged to the front blade sections, for change in pitch relative to the front sections, plus a rotary hub mounting the sectional propeller blades for rotation about the transverse axis, a circular normally stationary actuating member surrounding the transverse axis and mounted independently of the hub for variable tilting movement about an upright axis, means mounted on the hub for rotation and forward and backward movement and actuable by said circular actuating member to progressively increase and decrease the pitch of the flap blade sections relative to the front blade sections during rotation, and manually controlled means for adjusting the tilt of the circular actuating means about its upright axis, said mechanism including weight members mounted on the hub for lateral movement thereon and applying centrifugally developed forces to the forwardly and backwardly movable members and to the flap blade sections during rotation.

References Cited in the tile of this patent UNITED STATES PATENTS 1,325,696 Lightburne Dec. 23, 1919 1,419,877 Martel June 13, 1922 1,924,192 Kusse Aug. 29, 1933 2,023,760 Dornier Dec. 10, 1935 2,039,628 Brown May 5, 1936 2,489,343 Wasserman et a1. Nov. 29, 1949 2,510,006 Young May 30, 1950 

